Hi!
What I sometimes do, if something like that fails are the following two
things:
1.
ecasound -f:16,1,44100 -i mono-input.wav -f:16,2,44100 -o stereo-output.wav
-el:gverb,...
Or if this doesn't do it neither:
2.
sox -c 1 mono-input.wav -c 2 stereo-input.wav
This simply doubles the mono-channel. input still sounds mono, but can be
used with stereo-effects without a problem.
Kindest regards
Julien